The principal objective of this project is to reduce the mortality and morbidity of primary malignant melanoma of the skin of man. This objective is to be achieved through the establishment of the Malignant Melanoma Clinical Cooperative Group (MMCCG). This group is comprised of four participating groups (Harvard Medical School - Massachusetts General Hospital, Temple University School of Medicine, University of California Medical Center at San Francisco, and New York University Medical Center). During the year 73-74, for which funding is now sought under this feasibility grant, the MMCCG will formulate and adopt a computerized, standardized protocol to be used in the study of patients with primary malignant melanoma of the skin. In addition, the MMCCG will develop a standardized approach to clinical and pathologic diagnosis of malignant melanoma which will lead to a TNM system and to clinical staging of melanomas. This standardized approach to patients and their tumors will allow the evaluation of factors that indicate increased risk to acquire primary malignant melanoma of the skin (i.e., the "population-at-risk") and factors that may indicate which persons with localized primary cutaneous malignant melanoma are at risk to undergo dissemination (e.g., variations in host immunity). A further aim of the MMCCG is the education of physicians, the allied medical professions, and patients in the recognition of pre-invasive primary malignant melanoma of the skin. This approach to patients coupled with the education of physicians will result in a decreased mortality and morbidity of primary malignant melanoma.